REVIEW ARTICLE
Ceftazidime-Avibactam: a Novel Cephalosporin/b-lactamaseInhibitor Combination
George G. Zhanel • Christopher D. Lawson • Heather Adam • Frank Schweizer •
Sheryl Zelenitsky • Philippe R. S. Lagace-Wiens • Andrew Denisuik • Ethan Rubinstein •
Alfred S. Gin • Daryl J. Hoban • Joseph P. Lynch 3rd • James A. Karlowsky
Published online: 1 February 2013
� Springer International Publishing Switzerland 2013
Abstract Avibactam (formerly NXL104, AVE1330A) is
a synthetic non-b-lactam, b-lactamase inhibitor that
inhibits the activities of Ambler class A and C b-lacta-
mases and some Ambler class D enzymes. This review
summarizes the existing data published for ceftazidime-
avibactam, including relevant chemistry, mechanisms of
action and resistance, microbiology, pharmacokinetics,
pharmacodynamics, and efficacy and safety data from
animal and human trials. Although not a b-lactam, the
chemical structure of avibactam closely resembles portions
of the cephem bicyclic ring system, and avibactam has
been shown to bond covalently to b-lactamases. Very little
is known about the potential for avibactam to select for
resistance. The addition of avibactam greatly (4-1024-fold
minimum inhibitory concentration [MIC] reduction)
improves the activity of ceftazidime versus most species of
Enterobacteriaceae depending on the presence or absence
of b-lactamase enzyme(s). Against Pseudomonas aeru-
ginosa, the addition of avibactam also improves the
activity of ceftazidime (*fourfold MIC reduction). Lim-
ited data suggest that the addition of avibactam does not
improve the activity of ceftazidime versus Acinetobacter
species or most anaerobic bacteria (exceptions: Bacteroi-
des fragilis, Clostridium perfringens, Prevotella spp. and
Porphyromonas spp.). The pharmacokinetics of avibactam
follow a two-compartment model and do not appear to be
altered by the co-administration of ceftazidime. The max-
imum plasma drug concentration (Cmax) and area under the
plasma concentration-time curve (AUC) of avibactam
increase linearly with doses ranging from 50 mg to
G. G. Zhanel � H. Adam � F. Schweizer �P. R. S. Lagace-Wiens � A. Denisuik � E. Rubinstein �A. S. Gin � D. J. Hoban � J. A. Karlowsky
Department of Medical Microbiology, Faculty of Medicine,
University of Manitoba, Winnipeg, MB, Canada
G. G. Zhanel � E. Rubinstein
Department of Medicine, Health Sciences Centre,
Winnipeg, MB, Canada
G. G. Zhanel (&)
Clinical Microbiology, Health Sciences Centre, MS673-820
Sherbrook St., Winnipeg, MB R3A 1R9, Canada
e-mail: [email protected]
C. D. Lawson � S. Zelenitsky � A. S. Gin
Faculty of Pharmacy, University of Manitoba,
Winnipeg, MB, Canada
H. Adam � D. J. Hoban � J. A. Karlowsky
Department of Clinical Microbiology, Health Sciences Centre,
Winnipeg, MB, Canada
F. Schweizer
Department of Chemistry, Faculty of Science,
University of Manitoba, Winnipeg, MB, Canada
P. R. S. Lagace-Wiens
Department of Clinical Microbiology, Saint-Boniface General
Hospital, Winnipeg, MB, Canada
A. S. Gin
Department of Pharmacy, Health Sciences Centre,
Winnipeg, MB, Canada
J. P. Lynch 3rd
Division of Pulmonary, Critical Care, Allergy and Clinical
Immunology, The David Geffen School of Medicine at UCLA,
Los Angeles, CA, USA
Drugs (2013) 73:159–177
DOI 10.1007/s40265-013-0013-7
2,000 mg. The mean volume of distribution and half-life of
22 L (*0.3 L/kg) and *2 hours, respectively, are similar to
ceftazidime. Like ceftazidime, avibactam is primarily renally
excreted, and clearance correlates with creatinine clearance.
Pharmacodynamic data suggest that ceftazidime-avibactam
is rapidly bactericidal versus b-lactamase-producing Gram-
negative bacilli that are not inhibited by ceftazidime alone.
Clinical trials to date have reported that ceftazidime-
avibactam is as effective as standard carbapenem therapy
in complicated intra-abdominal infection and complicated
urinary tract infection, including infection caused by
cephalosporin-resistant Gram-negative isolates. The safety
and tolerability of ceftazidime-avibactam has been reported
in three phase I pharmacokinetic studies and two phase II
clinical studies. Ceftazidime-avibactam appears to be well
tolerated in healthy subjects and hospitalized patients, with
few serious drug-related treatment-emergent adverse
events reported to date.
In conclusion, avibactam serves to broaden the spectrum
of ceftazidime versus ß-lactamase-producing Gram-nega-
tive bacilli. The exact roles for ceftazidime-avibactam will
be defined by efficacy and safety data from further clinical
trials. Potential future roles for ceftazidime-avibactam
include the treatment of suspected or documented infec-
tions caused by resistant Gram-negative-bacilli producing
extended-spectrum ß-lactamase (ESBL), Klebsiella pneu-
moniae carbapenemases (KPCs) and/or AmpC ß-lacta-
mases. In addition, ceftazidime-avibactam may be used in
combination (with metronidazole) for suspected polymi-
crobial infections. Finally, the increased activity of ceft-
azidime-avibactam versus P. aeruginosa may be of clinical
benefit in patients with suspected or documented P. aeru-
ginosa infections.
1 Introduction
Broad-spectrum activity, well characterized pharmacoki-
netic and pharmacodynamic properties, and proven effi-
cacy and safety have made cephalosporins an important
part of the antimicrobial armamentarium for decades [1].
However, the worldwide spread of extended-spectrum
b-lactamases (ESBLs) [2], Klebsiella pneumoniae carba-
penemases (KPCs) [3], metallo-b-lactamases (MBLs) [3]
as well as the presence of chromosomal AmpC b-lacta-
mases [4] in Gram-negative bacilli has reduced the utility
of the cephalosporins and contributed to the increase in
difficult-to-treat multidrug-resistant (MDR) organisms [5].
Ceftazidime is a well described third-generation cephalo-
sporin with broad-spectrum activity against Gram-positive
cocci and Gram-negative bacilli, including Pseudomonas
aeruginosa; however, resistance—especially with Gram-
negative bacilli—is increasing globally [6–8].
Avibactam (NXL104, AVE1330A), patented in 2011, is
a non-b-lactam (diazabicyclooctane) [10] b-lactamase
inhibitor, is active in vitro against Ambler class A and C
b-lactamases and possesses activity versus some Ambler
class D enzymes [9, 10]. Avibactam is being developed in
combination with ceftazidime as well as in combination
with ceftaroline, with the aim of broadening the spectra of
these cephalosporins by inhibiting Ambler class A and C
b-lactamases. Ceftazidime-avibactam is currently in phase
III clinical trials for treatment of complicated urinary tract
infection and complicated intra-abdominal infection (http://
clinicaltrials.gov, identifiers NCT01595438, NCT01599
806, NCT01499290 and NCT01500239).
This article reviews the existing published data for
ceftazidime-avibactam, including relevant chemistry,
mechanisms of action, mechanisms of resistance, microbi-
ology, pharmacokinetics, pharmacodynamics, and efficacy
and safety data from animal and human trials. Literature for
this review was obtained via a comprehensive search of
MEDLINE, SCOPUS and databases of scientific meetings
from 2005 to September 2012 for all materials containing the
name ‘ceftazidime’ and any of ‘avibactam’, ‘NXL104’ or
‘AVE1330A’. These results were supplemented by bibliog-
raphies obtained from Novexel (http://www.novexel.com/
NXL104.htm) and AstraZeneca.
2 Chemistry
The cephem nucleus is a bicyclic ring system composed of
a four-member b-lactam ring fused with a six-member
dihydrothiazine ring, with a sulfur atom at position 1, a
double-bond between carbon 2 and carbon 3, and a car-
boxylic acid at position 4 [1, 11]. The distinct properties of
individual cephalosporins arise from side-chains attached
to the cephem nucleus at positions 3 and 7. The properties
conferred by particular cephalosporin side-chains have
been extensively reviewed [12–14].
Ceftazidime’s position 7 side-chain is an amino-acyl
group with an aminothiadiazole ring and a carboxypropyl-
oxyimino chain attached at the a-carbon (Fig. 1). The
aminothiadiazole ring, common to many extended-spec-
trum cephalosporins, confers increased activity against
Gram-negative bacilli. In comparison with the methoxy-
imino group frequently found in other third-generation
cephalosporins, the carboxypropyl-oxyimino group confers
similar stability to many b-lactamases, slightly decreased
activity towards the Enterobacteriaceae, but much-
increased activity versus P. aeruginosa [13–15]. The
methyl-pyridinium group at position 3 enhances activity
versus P. aeruginosa [12], and provides ceftazidime with
zwitterionic properties that enhance its water solubility
[11].
160 G. G. Zhanel et al.
The chemical structure of avibactam is (1R,2S,5R)-7-
oxo-6-(sulfoxy)-1,6-diazabicyclo[3.2.1]octan-2-carboxam-
ide [9] (Fig. 2) and it has a molecular weight of 265.25 Da.
Avibactam is a synthetic compound produced by an
enantio-selective process [9, 16]. Although not a b-lactam,
avibactam closely resembles b-lactams in key areas: the
carbonyl at avibactam position 7 mimics the b-lactam
carbonyl of a cephalosporin such as ceftazidime; the sulfate
at position 6 of avibactam takes the place of the carboxyl
group at ceftazidime position 4; and the carboxamide at
position 2 of avibactam aligns with the amino-acyl side-
chain at ceftazidime position 7 (Fig. 3). Avibactam is
synthesized as a sodium salt that is water soluble and stable
in aqueous solution at room temperature [17], but detailed
chemical data have not been published to date.
3 Mechanism of Action
Ceftazidime, like other b-lactams, inhibits peptidoglycan
synthesis by inhibiting penicillin-binding proteins (PBPs)
[18–20]. Inactivation of a sufficient fraction of the PBPs
leads to an unstable peptidoglycan cell wall, ultimately
resulting in cell death. Ceftazidime, by inhibiting pepti-
doglycan synthesis, inhibits growth of Escherichia coli and
P. aeruginosa at low concentrations and induces rapid lysis
in both species at higher concentrations [21].
b-lactamases are the most widespread and clinically
important contributor toward b-lactam resistance, particu-
larly among Gram-negative bacilli [4, 22, 23]. The b-lac-
tamases are commonly classified into groups A, B, C and D
based on similarity and difference in primary amino acid
sequence as described by Ambler and colleagues [24–27].
A second system that classifies the b-lactamases by spec-
trum of activity and resistance to b-lactamase inhibitors
was described by Bush and colleagues [28, 29], though the
molecular (Ambler) classification system is referred to in
this paper. The basic mechanism of action of b-lactamases
has been well described [30–32]. A common strategy to
inactivate b-lactamase activity is alteration of side-chains
to create a molecule for which the b-lactamase has poor
affinity (e.g. the 3 and 7 side-chains of the cephem
nucleus). A second effective strategy is the pairing of a
b-lactam with a b-lactamase inhibitor, a mechanistic or
suicide substrate that inactivates the b-lactamase in much
the same manner as the PBP is inactivated by a b-lactam.
As new b-lactams and b-lactamase inhibitors have been
introduced, selective pressure on clinical species express-
ing b-lactamases has driven their evolution such that for
any given b-lactam, a b-lactamase now exists that is
capable of inactivating it [28, 29]. A wide variety of
mutations alter the spectrum of existing b-lactamases to
increase their affinity for previously unaffected b-lactams
or render them resistant to existing b-lactamase inhibitors
[30, 33] (http://www.lahey.org/Studies/).
Avibactam has been shown to bond covalently to
b-lactamases through the formation of a carbamate bond
between avibactam’s position 7 carbonyl carbon and the
same active-site serine that participates in acyl bonding
with b-lactam substrates. The covalent nature of the bond
has been confirmed via determination of the x-ray crystal
structure of avibactam bound to a variety of b-lactamases
[34–38], representing all three molecular classes of serine
active site b-lactamases. Mass spectroscopy studies pro-
vide evidence that avibactam/b-lactamase binding involves
a simple reaction mechanism with no rearrangement like
that observed for molecules containing a b-lactam moiety
[39–41].
Studies assessing the half maximal inhibitory concen-
tration (IC50) values for avibactam have been measured and
N+
S167
8
54
2
3N
HH
O
NH
ON
O
O
OH
O−O
N
SH2N
H3C
CH3
Fig. 1 Chemical structure of ceftazidime
N
3
4
5
2
7 6
1
NO
SO
O
O−
O
O
H2N
Fig. 2 Chemical structure of avibactam
N+
S
N
HH
O
NH
ON
O
O
OH
O−O
N
SH2N
H3C
CH3
N
NO
S
O
O
O−
O
O
H2N
Fig. 3 Structural comparison of avibactam to ceftazidime
Ceftazidime-Avibactam 161
compared with clavulanic acid and tazobactam for a variety
of class A and C b-lactamases (Table 1) [40]. Although
IC50 values are time dependent [40], the values compiled in
Table 1 originate from experiments using similar method-
ology, allowing for useful comparison. Avibactam has
activity similar to that of clavulanic acid against SHV-4
and similar to that of both clavulanic acid and tazobactam
against CTX-M-15, but shows greater activity than (i.e. is a
more potent inhibitor) comparator inhibitors in all other
cases, particularly against the carbapenemase KPC-2 and
the class C b-lactamases.
A turnover value (indicating the number of inhibitor
molecules required to deactivate a single enzyme) of 1 has
been uniformly reported for avibactam (with one exception
[42]). The turnover rate of clavulanic acid is greater than
100-fold that of avibactam against TEM-1 [40], while that
of tazobactam is more than tenfold that of avibactam
against P99, and 50-fold that of avibactam when inhibiting
TEM-1 [40–42]. Initial studies reported an enzyme kinetic
model where inactivation of the b-lactamase enzyme
involved two binding steps: non-covalent association of
avibactam with the binding site followed by covalent
acylation of avibactam to the enzyme (along with opening
of the 5-member urea ring) [34, 40–42].
A recent paper by Ehmann et al. proposes that the
enzyme kinetics of avibactam are in fact that of a cova-
lently-binding reversible inhibitor with a two-step binding
process (as described above) and a slow deacylation phase
that restores avibactam’s 5-membered urea ring [39].
The work of Ehmann et al. supports the notion that
avibactam is released from the b-lactam in its original
form. This experiment was repeated with each of CTX-
M-15, KPC-2, P99 and the chromosomal AmpC of
P. aeruginosa inhibited by avibactam serving as a donor to
uninhibited TEM-1, with similar results [39]. Details of
reaction mechanism leading to the restoration of avibactam
as it is cleaved from the b-lactamase active site remain to
be discovered.
4 Mechanism of Resistance
Limited data exist regarding the potential for avibactam to
select for resistance and no data are available for ceftazi-
dime-avibactam. Avibactam has been reported to not induce
chromosomal ampC expression in Enterobacter cloacae
[43]. Livermore et al. [44] studied the consequences of
exposing Enterobacteriaceae to varying concentrations of
avibactam when used along with ceftaroline (an oxyimino-
cephalosporin). Single- and multi-step selection (where the
concentration of ceftaroline was doubled each step) was
performed and mutations were characterized by polymerase
chain reaction (PCR), DNA sequencing and SDS-PAGE
(sodium dodecyl sulfate polyacrylamide gel electrophore-
sis). Minimum inhibitory concentrations (MICs) of the pre-
and post-selection organisms were compared for a large
panel of b-lactam antibacterials. Single-step selection
experiments found that isolated colonies occurred at a
frequency of \10-9. An E. coli expressing a mutant
CTX-M-15 was found to have gained resistance to ceftar-
oline-avibactam but lost resistance to all non-ceftaroline
oxyimino cephalosporins through a point mutation in
blaCTX-M-15 leading to a Lys237Gln substitution. Two
AmpC-derepressed E. cloacae isolates were found to have
identical deletions in ampC, gaining resistance to ceftaro-
line-avibactam with no loss of resistance to other agents.
The MICs for three derepressed-AmpC E. cloacae were
doubled six times against ceftaroline plus 1 mg/L avibac-
tam, and four or five times against ceftaroline plus 4 mg/L
avibactam. One E. cloacae mutant lacked the porins OmpC
and OmpF but showed no other mutation, while the
remaining mutants showed point mutations at the same
location in ampC leading to Asn366His (in a mutant also
showing reduced porin expression) and Asn366Ile substi-
tutions. In experiments assessing the activity of several
b-lactamase inhibitors against functional CMY-2 b-lacta-
mase mutants, the affinity of avibactam for mutant enzymes
was found to decrease, but this did not result in a reduction
of in vitro antimicrobial activity [45, 46]. Clearly, infor-
mation on potential mechanisms of resistance to avibactam
are limited and no data exist with ceftazidime-avibactam,
thus work is required in this area.
Table 1 Half maximal inhibitory concentration values for avibactam
and comparator b-lactamase inhibitors determined after 5 min of
incubation with different b-lactamases
b-lactamase inhibitor IC50 (nM) Reference
Avibactam Clavulanic acid Tazobactam
Class A
TEM-1 8 130 40 [42]
TEM-1 8 58 32 [41]
SHV-4 1.5 5 120 [79]
SHV-4 3 4 55 [41]
KPC-2 38 6,500 80,000 [82]
KPC-2 37.5 ± 2.6 6,500 ± 400 9,200 ± 4,100 [78]
KPC-2 170 [100,000 50,000 [41]
CTX-M-15 4.5 ± 0.9 12.5 ± 2.8 5.8 ± 2.7 [78]
CTX-M-15 5 12 6 [34]
CTX-M-15 5 12 6 [41]
Class C
P99 80 1 9 106 5,000 [42]
P99 100 [100,000 1,300 [41]
AmpC 128 [100,000 4,600 [41]
IC50 Half maximal inhibitory concentration
162 G. G. Zhanel et al.
5 Microbiology
The MIC50, MIC90 and MIC range values (mg/L) presented
in Tables 2, 3 and 4 are modal values derived from a
review of available published literature for ceftazidime-
avibactam and comparators to date. Table 2 shows the
activity of ceftazidime-avibactam and comparators against
Gram-negative bacteria [47–66]. These data demonstrate
that the addition of avibactam greatly improves (4-1024-
fold MIC reduction) the activity of ceftazidime versus most
Enterobacteriaceae species depending on the presence or
absence of a b-lactamase enzyme(s). Against P. aerugin-
osa, the addition of avibactam improves the activity of
ceftazidime (*fourfold MIC90 reduction) [Table 2]. Lim-
ited data suggest that the addition of avibactam does not
improve the activity of ceftazidime versus Acinetobacter
species (Table 2).
Table 3 shows the activity of ceftazidime-avibactam
compared with ceftazidime alone against E. coli and
K. pneumoniae isolates producing specific b-lactamase
enzymes [42, 47, 57, 58, 67–83]. It should be noted that,
except where indicated, MIC values are based on results
from fewer than ten isolates. Although the effect of avi-
bactam was consistent when larger sample sizes were
available, results derived from smaller numbers of isolates
should be interpreted cautiously. Avibactam significantly
improved the activity of ceftazidime against both E. coli
and K. pneumoniae-producing ESBLs from Ambler classes
A (4-1024-fold MIC reduction) and D (2-512-fold MIC
reduction), KPC carbapenemases (32-8192-fold MIC
reduction) and both chromosomal and mobile Ambler class
C b-lactamases (2-512-fold MIC reduction). As expected,
given its mechanism of action, avibactam does not improve
the activity of ceftazidime against organisms producing
MBLs such as New Delhi MBL (NDM) [Table 3]. It needs
to be stated that the majority of Enterobacteriaceae with
elevated ceftazidime-avibactam MIC values will likely
contain multiple resistance mechanisms, which may
include b-lactamases not inhibited by avibactam (i.e. some
OXA-types and MBLs), porin alterations and overexpres-
sion of efflux pumps.
The activity of ceftazidime-avibactam and comparators
against anaerobic bacteria is presented in Table 4 [84–86].
Versus Bacteroides fragilis, Clostridium perfringens and
organisms from the Prevotella and Porphyromonas genera,
ceftazidime-avibactam significantly increased the activity
compared with ceftazidime alone. For other anaerobes,
ceftazidime-avibactam showed little or no improvement
over that of ceftazidime alone; most MIC50 values and all
MIC90 values remained above the Clinical and Laboratory
Standards Institute (CLSI) resistant breakpoint for ceftaz-
idime (C32 mg/L). No data have been published on the
activity of ceftazidime-avibactam versus Gram-positive
bacteria.
6 Pharmacokinetics
The pharmacokinetics of ceftazidime are well known.
Following a 1 g dose (infused over 30 min), the concen-
tration profile is best described by a two-compartment
model with a rapid distribution phase, a maximum plasma
drug concentration (Cmax) of *100 mg/L, and a volume of
distribution (Vd) of *0.3 L/kg [1, 87]. Ceftazidime is
approximately 17 % protein bound, is 80–90 % renally
cleared with an elimination half-life (t�) of approximately
1.8 h in patients with normal renal function [1, 87]. Data
on the interaction of ceftazidime with avibactam was
published for 16 healthy volunteers [88]. Two cohorts of
eight subjects were administered single doses of 250 mg or
500 mg of avibactam, followed (after a 7-day washout
period) by a ceftazidime-avibactam dose of 1,000/250 mg
and 2,000/500 mg, respectively. The presence of ceftazi-
dime was not found to affect the pharmacokinetics of
avibactam and, in the presence of avibactam, the pharma-
cokinetics of ceftazidime were unchanged.
The results of three phase I trials examining the single-
dose pharmacokinetics of avibactam ranging from 50 mg
to 2,000 mg are summarized in Table 5. In a single dose
escalation study involving 70 subjects, the pharmacoki-
netics of avibactam were reported as linear for doses from
50 mg to 2,000 mg (Table 5) [88, 89, 91]. Following a
100-mg dose (infused over 30 min), the concentration
profile of avibactam is best described by a two-compart-
ment model with a rapid distribution phase, a Cmax of
*5.0 mg/L and a Vd at steady state (Vss) of *22.5 L [88,
91]. To date, the protein binding of avibactam is unknown;
avibactam, like ceftazidime, is primarily (95 %) renally
cleared, with clearance correlating well with creatinine
clearance (CLCR) [89]. The phase I studies in healthy
volunteers describe an average half-life of 1.7–2.1 h. The
study of avibactam in complicated intra-abdominal infec-
tion reported a 62 % increase in avibactam clearance
compared with healthy subjects [90].
In six anuric patients, a pharmacokinetic study of
100 mg of avibactam administered over 30 mins prior to
haemodialysis (4-h session) found a mean extraction
coefficient of 0.77, with a total clearance of 9.29 L/h
(155 mL/min), and approximately 54 % of the drug
removed during dialysis, which is similar to ceftazidime
[91]. In the same patient cohort, the average clearance off-
dialysis was 1.02 L/h (17 mL/min) with a t� of 22.2 h.
In summary, the pharmacokinetics of avibactam and
ceftazidime appear to be very complementary, with similar
Ceftazidime-Avibactam 163
Ta
ble
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21
28
83
26
4[
64
Am
pC
hy
per
-pro
du
cin
g1
66
40
.12
–[6
40
.12
0.5
B0
.00
4–
41
28
0.2
50
.58
32
ES
BL
pro
du
cin
gan
dA
mp
Ch
yp
er-p
rod
uci
ng
32
[6
42
–[6
40
.12
0.1
20
.01
5–
0.1
2[
51
21
63
2[
64
[6
4
Kle
bsi
ella
oxy
toca
B0
.25
0.5
B0
.25
–[6
40
.12
0.5
B0
.06
–1
1B
1B
1B
0.2
50
.5
Kle
bsi
ella
pn
eum
on
iae
B0
.25
1B
0.5
–[3
20
.12
0.5
B0
.06
–2
2B
1B
1B
0.2
5B
0.2
5
ES
BL
pro
du
cin
g6
4[
64
0.1
2–
25
60
.51
0.0
6–
2[
64
86
4[
64
[6
4
OX
A-4
8ca
rbap
enem
ase-
pro
du
cin
g2
56
51
2B
0.1
2–
51
20
.25
0.5
\0
.00
8–
11
02
43
25
12
NA
NA
KP
C-p
rod
uci
ng
C5
12
C5
12
32
–C
51
20
.25
1B
0.0
6–
1C
51
23
21
28
NA
NA
ES
BL
-pro
du
cin
gp
lus
po
rin
loss
25
65
12
12
6–
51
21
10
.5–
25
12
NA
NA
NA
NA
Kle
bsi
ella
spp
.0
.12
32
NA
0.1
20
.5B
0.0
3–
32
64
B0
.12
16
0.0
63
2
ES
BL
[3
2[
32
NA
0.5
2B
0.0
3–
32
[1
6[
16
[1
6N
AN
A
Car
bap
enem
no
n-s
usc
epti
ble
c[
32
[3
2N
A0
.52
B0
.03
–3
2[
16
[1
6[
16
NA
NA
Mo
rga
nel
lam
org
an
ii0
.12
8N
A0
.06
0.1
2B
0.0
6–
86
4B
0.1
20
.25
0.1
28
Pro
teu
sm
ira
bil
is0
.06
0.1
2B
0.2
5–
32
0.0
60
.12
B0
.03
–0
.25
1B
0.1
20
.25
B0
.25
B0
.25
Ind
ole
-po
siti
ve
Pro
teu
ssp
p.
0.1
28
NA
0.0
60
.25
B0
.03
–2
32
B0
.12
0.2
5N
AN
A
Sa
lmo
nel
lasp
p.
0.2
50
.5N
A0
.25
0.5
B0
.03
–0
.51
B0
.12
0.2
50
.06
0.1
25
Ser
rati
am
arc
esce
ns
0.1
22
B0
.25
–1
60
.25
0.5
B0
.06
–[8
4B
0.1
22
B0
.25
1
Ser
rati
asp
p.
0.2
50
.5N
0.2
50
.50
.06
–8
1B
0.1
20
.5N
AN
A
Bu
rkh
old
eria
cep
aci
a6
4[
12
88
–[1
28
8[
12
8B
1–[
12
81
NA
NA
NA
NA
Pse
ud
om
on
as
aer
ug
ino
sa4
32
B0
.25
–2
56
28
B0
.06
–[1
28
44
16
32
[6
4
MD
Rd
NA
83
2B
1–[
12
8N
AN
AN
AN
AN
A
Am
pC
-der
epre
ssed
64
[1
28
8–[
12
84
8B
1–
64
[1
6N
AN
AN
AN
A
Intr
insi
cM
exA
/Op
rM4
8B
1–
16
48
B1
–1
61
NA
NA
NA
NA
Aci
net
ob
act
erb
au
ma
nn
ii8
32
1–[
51
28
[1
61
–2
56
NA
64
12
88
64
OX
Aca
rbap
enem
ase-
pro
du
cin
g1
28
[1
28
4–[
12
88
[1
28
4–[
12
81
NA
NA
NA
NA
164 G. G. Zhanel et al.
Vd, t� and clearance. The administration of ceftazidime
does not impact the pharmacokinetics of avibactam.
7 Pharmacodynamics
The comparative results of an in vitro time kill study
examining the bactericidal activity of ceftazidime in
combination with avibactam against a variety of b-lacta-
mase-producing genotypes are summarized in Table 6
[70]. In this study, ceftazidime alone was not bactericidal
except at 256 mg/L against the K. pneumoniae expressing
SHV-11, a non-ESBL. The comparator ceftazidime-clav-
ulanic acid (ratio of 4:1) was only bactericidal against one
E. cloacae isolate (at 32 mg/L), while the comparator
piperacillin/tazobactam (ratio 8:1) was not bactericidal
against any isolate at concentrations between 16 mg/L and
256 mg/L. In contrast, ceftazidime-avibactam proved to be
bactericidal versus all strains at concentrations ranging
from 2 to 8 mg/L (Table 6).
The bactericidal activity of two ceftazidime-avibactam
dosing regimens was studied against a variety of b-lacta-
mase-producing genotypes, in an in vitro pharmacodynamic
hollow-fibre model [67]. Both regimens maintained a con-
tinuous infusion of ceftazidime at 16 mg/L, with regimen 1
adding a continuous infusion of avibactam at 4 mg/L, while
regimen 2 added a single dose of avibactam (both with a
2-h half-life). Both regimens were tested against an
E. cloacae isolate expressing AmpC, a K. pneumoniae
isolate expressing CTX-M-15, and two K. pneumoniae
isolates expressing SHV-5 and TEM-10, respectively. With
ceftazidime alone, all four isolates demonstrated MICs
[128 mg/L, ceftazidime-avibactam MICs were B4 mg/L
for all isolates. For all isolates, the total area under the
plasma concentration-time curve (AUC) of avibactam was
either similar for both regimens or higher in regimen 2.
Versus all isolates studied, both combinations of ceftazi-
dime-avibactam were bactericidal ([3 log10 bacterial kill)
within 2 h. Regarding regrowth, no regrowth was observed
with regimen 1; however, regrowth was observed for all
four isolates with regimen 2 after the concentration of avi-
bactam dropped below the limit of detection of 0.5 mg/L.
No change in pre- and post-experiment MIC occurred with
any isolate treated with ceftazidime-avibactam.
An in vitro study examined the bactericidal activity of
2,000 mg ceftazidime dosed three times per day plus avi-
bactam dosed as a continuous infusion with concentrations
of 0.5, 1, 2, 4, 6, 8 or 10 mg/L over the course of 72 h
versus a strain of Amp-C hyperproducing E. cloacae
(ceftazidime-avibactam MIC of 0.5 mg/L, avibactam fixed
at 2 mg/L) [92]. Bactericidal activity was monitored by
change in viable colony counts and area under the bacte-
rial kill curve. Ceftazidime-avibactam was bactericidalTa
ble
2co
nti
nu
ed
Gra
mn
egat
ive
aero
be
Cef
tazi
dim
eC
efta
zid
ime-
avib
acta
ma
Cef
tazi
dim
e-
avib
acta
mM
IC90
red
uct
ion
(fo
ld)
Cef
epim
eC
eftr
iax
on
e
MIC
50
MIC
90
Ran
ge
MIC
50
MIC
90
Ran
ge
MIC
50
MIC
90
MIC
50
MIC
90
Aci
net
ob
act
ersp
p.
[3
2[
32
NA
16
[3
2B
0.0
3–[
32
1[
16
[1
61
6[
32
Imip
enem
-res
ista
nte
[3
2[
32
NA
32
[3
20
.25
–[3
21
[1
6[
16
NA
NA
aF
ixed
avib
acta
mco
nce
ntr
atio
no
f4
mg
/Lb
Cef
tazi
dim
eM
ICC
32
mg
/Lc
Mer
op
enem
MIC
C8
mg
/L;
imip
enem
MIC
C8
mg
/Ld
MD
Rd
efin
edas
con
com
itan
tre
sist
ance
toth
ree
or
mo
red
iffe
ren
tan
tim
icro
bia
lcl
asse
se
Imip
enem
MIC
C1
6m
g/L
ES
BL
exte
nd
ed-s
pec
tru
mß
-lac
tam
ase,
KP
CK
leb
siel
lap
neu
mo
nia
eca
rbap
enem
ases
,M
DR
mu
ltid
rug
resi
stan
t,M
IC50
min
imu
mco
nce
ntr
atio
nto
inh
ibit
gro
wth
of
50
%o
fis
ola
tes,
MIC
90
min
imu
mco
nce
ntr
atio
nto
inh
ibit
gro
wth
of
90
%o
fis
ola
tes
Ceftazidime-Avibactam 165
Table 3 In vitro activity of ceftazidime-avibactam and comparators against bacteria expressing specific b-lactamase enzymes [42, 47, 57, 58,
67–83]
b-lactamase enzymea MIC MIC reduction (fold)
Ceftazidime Ceftazidime-avibactamb
Escherichia coli
Extended-spectrum b-lactamases CTX-M-9 2 0.25 8
CTX-M-14 2 0.06 32
CTX-M-15c 32 0.12 256
PER-1 256 1 256
SHV-3 32 0.06 512
SHV-4 128 0.25 512
SHV-5 64 0.25 256
TEM-3 64 0.25 256
TEM-5 32 0.06 512
TEM-6 [128 0.5 [256
TEM-7 16 1 16
TEM-8 256 0.25 1024
TEM-9 [128 0.5 [256
TEM-10 128 0.5 256
TEM-12 16 0.25 64
TEM-16 256 0.5 512
TEM-24 [64 4 [16
TEM-43 4 0.25 16
OXA-2 0.25 0.12 2
OXA-48 4 B0.008 C512
CTX-M-2, TEM-1 32 0.5 64
CTX-M-15, TEM-1c 32 0.12 256
CTX-M-15, OXA-1c 16 0.25 64
CTX-M-16, TEM-1c [128 1 [128
SHV-12, TEM-1 16 0.06 256
CTX-M-15, TEM-1, OXA-1c 128 0.25 512
Carbapenemases KPC-2 64 0.25 256
KPC-2, TEM-1 128 0.5 256
KPC-3 64 2 32
GES-3 128 0.25 512
GES-4 128 1 128
Metallo-b-lactamases NMC-A 0.25 B0.015 C16
PER-1 [64 4 [16
VEB-1 2 0.5 4
IMP-1 256 64 4
NDM [256 [256 [1
VIM-1 [512 512 [1
Ambler class C b-lactamases AmpC 16 1 16
AmpC, CTX-M-15 [32 0.12 [56
AmpC, CTX-M-15, OXA-1, TEM-1 [32 0.25 [128
ACC-1 [64 4 [16
CMY-2, VEB-2 256 128 2
CMY-2, CTX-M-14, TEM-1 128 1 128
CMY-2, CTX-M-15, OXA-1 32 0.06 512
FOX-1 32 4 8
166 G. G. Zhanel et al.
(C3 log10) for all concentrations of avibactam. Regrowth
was observed with all concentrations of avibactam. Whe-
ther this was due to low ceftazidime or avibactam con-
centrations was unknown; however, sigmoid curves fit at
12, 24, 48 and 72 h for change in viable colony count, and
at 24, 48 and 72 h for area under the bacterial kill curve (r2
0.67 to 0.99), indicated that no additional benefit was
gained from avibactam concentrations [2 mg/L.
Human plasma samples containing ceftazidime-avibac-
tam were collected from a phase I pharmacokinetic and
safety evaluation study and assessed in vitro for bacteri-
cidal activity against 5 9 105 colony-forming units (CFUs)
of two K. pneumoniae strains: one ceftazidime-susceptible
and one ceftazidime-resistant expressing AmpC and SHV-
11 b-lactamases [88]. Plasma samples from eight subjects
dosed with 1,000/250 mg ceftazidime-avibactam and eight
subjects dosed with 2,000/500 mg ceftazidime-avibactam
were found to be bactericidal (minimum of 3 log10
reduction from the initial inoculum count) versus both
strains.
Table 3 continued
b-lactamase enzymea MIC MIC reduction (fold)
Ceftazidime Ceftazidime-avibactamb
Klebsiella pneumoniae
Extended-spectrum b-lactamases CTX-M-3 16 0.5 32
CTX-M-14 16 1 16
CTX-M-15c [128 1 [128
SHV-2 [64 0.5 [128
SHV-3 [64 0.5 [128
SHV-4 [256 4 [64
SHV-5 64 0.5 128
SHV-6 4 1 4
SHV-18 64 2 32
SHV-38 8 2 4
TEM-4 32 0.5 64
CTX-M-2, TEM-1B 128 2 64
CTX-M-16, OXA-1 256 1 256
SHV-5, TEM-10 [128 2 [64
CTX-M-2, SHV-5, TEM-12 [128 2 [64
CTX-M-2, SHV-2, TEM-12 [128 4 [32
CTX-M-3, SHV-1, TEM-1B 256 2 128
CTX-M-15, TEM-1, OXA-1 256 2 128
SHV-1, TEM-2, PER 256 4 64
Carbapenemases KPC-2c [128 1 [128
KPC-3c 256 0.5 512
KPC-2, SHV-11, SHV-12, TEM-1 512 B0.06 C8192
Metallo-b-lactamases VIM-1, SHV-5 256 256 1
Ambler class C b-lactamases AmpC ? SHV-11 64 2 32
DHA-2 256 2 128
ACC-1, TEM-1 128 1 128
LAT-4, SHV-11 variant 32 1 32
CMY-4, TEM-1 256 0.5 512
DHA-1, SHV-2a, TEM-1 [128 1 [128
MOX-2, SHV-5, TEM-1 256 1 256
a Isolates may contain genes encoding other b-lactamasesb Fixed avibactam concentration of 4 mg/Lc Modal MIC values derived from MIC data for ten or more unique isolates
MIC minimum inhibitory concentration
Ceftazidime-Avibactam 167
8 Animal Studies
Two studies have reported the efficacy of ceftazidime-
avibactam in murine septicaemia. In the first study, female
CD-1 mice were infected with 3.3 to 3.6 9 105 CFU of two
strains of KPC-producing K. pneumoniae (strain VA-361
expressing KPC-2, TEM-1 and SHV-11 with ceftazidime
MIC 256 mg/L, or strain VA-406 expressing KPC-2,
TEM-1, SHV-11 and SHV-12 with ceftazidime MIC
C512 mg/L) via intraperitoneal injection [93]. Single doses
of ceftazidime-avibactam (ratios of 2:1, 4:1, 8:1 and 16:1;
ceftazidime doses, depending on strain and ratio, from 1 to
64 mg/kg by twofold steps) or ceftazidime alone (512,
1,024 or 2,048 mg/kg) were administered subcutaneously
30 minutes after infection. Five mice were tested per dose,
survival rate was monitored twice daily for 5 days, and all
tests were performed in triplicate. Untreated mice died
within 24 to 48 hours. For ceftazidime alone, effective dose
in 50% (ED50) was 1,578 mg/kg for strain VA-261 and
709 mg/kg for strain VA-406, whereas for ceftazidime-
avibactam, ED50 values were significantly reduced at 8.1,
15.1, 16.9 and 29.5 mg/kg (ceftazidime component) for
strain VA-261, and 3.5, 3.8, 7.2 and 12.1 mg/kg for strain
VA-406 for ceftazidime-avibactam ratios of 2:1, 4:1, 8:1
and 16:1, respectively. At any given dose, animal survival
was observed to increase as the proportion of avibactam in
ceftazidime-avibactam increased.
In the second septicaemia study, male CD-1 mice were
infected with 108 CFU of one of four ceftazidime-resistant
strains (E. coli expressing CTX-M-16 and TEM-1; E. coli
expressing CTX-M-2 and TEM-1; K. pneumoniae
expressing CTX-M-2, SHV-2 and TEM-12; K. pneumoniae
expressing CTX-M-2 and TEM-1B, all with ceftazidime
MICs from 32 to [128 mg/L) by intraperitoneal injection
[71]. Infected mice were administered subcutaneous doses
at 1 and 4 h post-infection with one of ceftazidime-avi-
bactam (4:1 ratio, ceftazidime doses 3, 10 and 30 mg/kg),
ceftazidime (doses 3, 10, 30 and 60 mg/kg), cefotaxime
(doses 3, 10, 30, 60 and 90 mg/kg) or piperacillin/tazo-
bactam (4:1 ratio, piperacillin doses 30, 60 and 90 mg/kg).
Ten to twenty mice were infected per strain per dose reg-
imen, and survival was monitored for 5 days. Untreated
mice died within 2 days. For ceftazidime-avibactam, ED50
values were reported as 11 mg/kg/dose (for the ceftazidime
component) for the E. coli strain expressing CTX-M-16
and TEM-1, 27 mg/kg/dose for the E. coli strain expressing
CTX-M-2 and TEM-1, 27 mg/kg/dose for the K. pneumo-
niae strain expressing CTX-M-2, SHV-2 and TEM-12, and
18 mg/kg/dose for the K. pneumoniae strain expressing
CTX-M-2 and TEM-1B. ED50 values for all comparators
for all strains were[90 mg/kg/dose except for ceftazidime
alone against the E. coli strain expressing CTX-M-16 and
TEM-1, with an ED50 of 74 mg/kg/dose.
In a murine kidney infection model study, male CD-1
mice were infected with approximately 104 CFU of one of
six ceftazidime-resistant strains (E. coli expressing SHV-4,
E. coli expressing AmpC, E. cloacae expressing AmpC,
K. pneumoniae expressing AmpC and SHV-11, Morgan-
ella morganii expressing AmpC, or Citrobacter freundii
expressing AmpC, all with ceftazidime MICs from 16 to
[128 mg/L) via direct injection to the left kidney [68].
Infected mice were treated at 4, 8, 24 and 32 h after
Table 4 In vitro activity of ceftazidime-avibactam and comparators versus anaerobic bacteria [84–86]
Anaerobic bacteria Ceftazidime Ceftazidime-avibactama Ceftazidime-
avibactam MIC90
reduction (fold)
Ceftriaxone
MIC50 MIC90 Range MIC50 MIC90 Range MIC50 MIC90
Bacteroides caccae [128 [128 8–[128 32 [128 4–[128 1 NA NA
Bacteroides fragilis 64 [128 0.5–[128 4 32 B0.06–[64 [4 16 128
Bacteroides ovatus [128 [128 8–[128 128 [128 32–[128 1 [64 [64
Bacteroides stercoris/uniformis/salyersiae [128 [128 32–[128 64 128 4–[128 [1 32 [128
Bacteroides thetaiotaomicron [128 [128 [128 128 [128 16–[128 1 [64 [64
Bacteroides vulgatus [128 [128 32–[128 32 128 16–128 [1 16 [64
Bacteroides spp. 128 [128 0.5–[128 8 64 B0.06–[64 [2 64 [128
Parabacteroides spp. [128 [128 8–[128 16 64 4–[128 [2 NA NA
Clostridium difficile 128 [128 64–[128 32 64 32–[128 [2 32 128
Clostridium perfringens 64 [128 0.5–[128 B0.06 2 B0.06–4 [64 0.5 2
Fusobacterium spp. NA NA 0.125–32 NA NA B0.06–2 NA NA NA
Prevotella/Porphyromonas spp. 32 [128 0.5–[128 2 4 B0.125–8 [32 NA NA
Gram-positive anaerobes 1 64 B0.06–32 0.25 32 B0.06–16 2 1 64
a Fixed avibactam concentration of 4 mg/L
MIC50 minimum concentration to inhibit growth of 50 % of isolates, MIC90 minimum concentration to inhibit growth of 90 % of isolates, NA No
data available
168 G. G. Zhanel et al.
infection with one of ceftazidime-avibactam (ratio 4:1),
ceftazidime alone, ceftazidime/clavulanic acid (ration 4:1,
10 or 25 mg/kg/dose for all ceftazidime components) or
imipenem (10 or 25 mg/kg/dose). Four mice were infected
per dose group or control group, control groups were
euthanized at 4 and 48 h, and test mice were euthanized at
48 h. At 10 mg/kg/dose, ceftazidime was ineffective at
eradicating the pathogen from the kidney versus the E. coli
strain expressing AmpC and the C. freundii strain. Ceftazi-
dime-avibactam (10 mg/kg/dose) was significantly more
effective than ceftazidime alone against the AmpC-
expressing E. coli. Ceftazidime-avibactam (10 mg/kg/dose)
and imipenem (10 mg/kg/dose) were significantly more
effective than ceftazidime alone against the C. freundii
strain. At 25 mg/kg/dose, ceftazidime was ineffective against
the SHV-4-expressing E. coli strain and the E. cloacae,
K. pneumoniae and M. morganii strains. Ceftazidime/
clavulanic acid (25 mg/kg/dose) was significantly more
effective than ceftazidime alone against the SHV-4-
expressing E. coli strain and the M. morganii strain, and both
Table 6 In vitro bactericidal activity of ceftazidime/avibactam by time kill assay [70]
Species Resistance
phenotype
Ceftazidime
MIC (mg/L)
Ceftazidime/avibactama
MIC (mg/L)
Minimum bactericidal
concentration of
ceftazidime/avibactamb (mg/L)
Citrobacter freundii TEM-1 and AmpC 64 2 2
C. freundii Derepressed AmpC [32 2 4
Enterobacter cloacae Derepressed AmpC [64 4 4
E. cloacae Derepressed AmpC [128 4 4
E. cloacae Derepressed AmpC [64 4 8
Klebsiella pneumoniae DHA-2 [256 4 4
K. pneumoniae LAT-4 and SHV-11 variant 32 1 4
K. pneumoniae SHV-4 [256 4 2
K. pneumoniae SHV-11 32 4 2
a 4:1 ratio ceftazidime/avibactamb A 3 log10 reduction of the initial colony count was considered bactericidal
MIC minimum inhibitory concentration
Table 5 Results from phase I pharmacokinetic studies of avibactam in healthy human subjects
Subject Demographics n Type of
study
Dose
(mg)
Cmax (mg/L)a AUC
(mg � h/L)aVss (L)a t1/2 (h)a CL
(mL/min)aReference
Young healthy adult
malesb70 Single
escalating
dosee
50 2.67 ± 0.37 3.72 ± 0.41 22.5 ± 2.0 1.99 ± 0.42 206.9 ± 19.9 [88]
100 5.09 ± 1.68 8.36 ± 1.67
250c 12.1 ± 2.4 19.7 ± 2.2
500d 29.0 ± 16.8 38.5 ± 10.4
1,000 49.6 ± 10.9 87.1 ± 13.9
1,500 101 ± 21 146 ± 15
2,000 124 ± 29 186 ± 28
Healthy males, mean age
28.7 years (range 20–37)
8 Single dosee 500 33.83 ± 4.24 49.86 ± 6.27 NR 2.09 ± 0.64 169.3 ± 20.5 [88]
Healthy females, mean age
20.9 years (range 23–44)
8 Single dosee 500 36.86 ± 9.31 49.75 ± 9.10 NR 1.71 ± 0.09 172.3 ± 30.3 [88]
Healthy malesb 6 Single dosee 100 4.66 ± 0.36 6.89 ± 0.56 NR 1.79 ± 0.32 243.3 ± 19.2 [91]
a Mean ± standard deviationb Demographic details not availablec Administered alone and separately with 1,000 mg of ceftazidimed Administered alone and separately with 2,000 mg of ceftazidimee 30-minute intravenous infusion
AUC area under the plasma concentration-time curve, CL clearance, Cmax maximum plasma drug concentration, NR value not reported,
t� elimination half-life, Vss volume of distribution at steady state
Ceftazidime-Avibactam 169
ceftazidime-avibactam (25 mg/kg/dose) and imipenem
(25 mg/kg/dose) were significantly more effective than ce-
ftazidime alone against all four strains. Bacterial load in the
kidney in mice receiving ceftazidime-avibactam was 2.6 to
4.5 log10 lower than the bacterial load in mice receiving
ceftazidime alone.
In a neutropenic murine thigh infection model study,
female CD-1 mice were infected with 106 CFU of two strains
of KPC-producing K. pneumoniae (strain VA-361 express-
ing KPC-2, TEM-1 and SHV-11 with ceftazidime MIC
256 mg/L, and strain VA-406 expressing KPC-2, TEM-1,
SHV-11 and SHV-12 with ceftazidime MIC C512 mg/L) via
intramuscular injection in the right thigh [93]. Mice were
treated 1.5 hours after infection with a single subcutaneous
dose of ceftazidime-avibactam (4:1 ratio with doses of the
ceftazidime component ranging by twofold steps from 32 to
1,024 mg/kg for strain VA-361, and 8 to 1,024 mg/kg for
strain VA-406) or ceftazidime alone (1,024 mg/kg or
2,048 mg/kg). Three mice were tested per dose and control
group, treatment mice were euthanized and analysed 24 h
after infection, and control mice were euthanized and ana-
lysed 1.5 and 24 h after infection. Doses resulting in bacte-
riostasis using ceftazidime-avibactam were 216/54 mg for
strain VA-361 and 116/29 mg for strain VA-406.
In a second human-simulated study of murine thigh
infection in both immunocompromised (cyclophosphamide-
induced neutropenia) and immunocompetent mice, immu-
nocompromised mice were infected with one of 27 strains of
P. aeruginosa in triplicate, and immunocompetent mice were
infected with one of 15 strains in triplicate [94]. Ceftazidime-
avibactam MICs ranged from 4 to 32 mg/L and all but one
isolate was non-susceptible to ceftazidime alone (MICs
ranging from 8 to[128 mg/L). Human simulated regimens
of ceftazidime or ceftazidime-avibactam beginning 2 h after
inoculation were administered. Simulated regimens were
pharmacokinetically assessed to closely match human dosing
of 2 g ceftazidime or 2 g ceftazidime plus 500 mg avibactam
every 8 h. By analysis of post-treatment bacterial loads, the
authors reported that the in vivo activity was pharmacody-
namically predictable based on the MIC of the strain to the
drug tested. Ceftazidime decreased bacterial counts by C0.5
log10 in only 10/27 isolates; while ceftazidime avibactam did
so in 22/27 of the P. aeruginosa strains. In the immuno-
competent mice, ceftazidime achieved reductions of C0.3
log10 in 10/15 isolates, while ceftazidime-avibactam did so
against all 15 isolates [94].
In a murine pneumonia model study, immunosuppressed
female Swiss OF1 mice were infected intratracheally with
108 to 109 CFU of a LAT-4 and SHV-11-producing strain of
K. pneumoniae [75]. Mice were treated twice per day for
2 days with subcutaneous doses of 2:1 ceftazidime-avi-
bactam (150/75 mg/kg), 4:1 ceftazidime-avibactam (150/
37.5 mg/kg), ceftazidime (150 mg/kg), 2:1 ceftazidime/
clavulanic acid (150/75 mg/kg), 4:1 ceftazidime/clavulanic
acid (150/37.5 mg/kg) or 1:1 imipenem/cilastatin (150 mg/
kg each) beginning 16–18 hours after infection. Thirty mice
were tested per treatment group, 20 mice were tested per
control group, and lung bacterial burden was assessed at 24
and 48 h after initiation of treatment. Untreated mice died
within 48 h of infection. Compared with treatment with
ceftazidime alone, lung bacterial burden was significantly
reduced at 48 h by the 2:1 and 4:1 ceftazidime-avibactam
regimens and the imipenem/cilastatin regimen (p \ 0.05 in
all cases). A CFU reduction of 6.6 ± 1.0 log10 was found
for the 2:1 ceftazidime-avibactam regimen and 7.9 ± 0.1
log10 for the 4:1 ceftazidime-avibactam regimen compared
with a 0.7 ± 1 log10 reduction for ceftazidime alone.
In a rabbit meningitis model study, pathogen-free New
Zealand rabbits were infected via direct injection to the
subarachnoid space of approximately 105 CFU of an
AmpC-producing K. pneumoniae strain (ceftazidime MIC
[128 mg/L) [69]. Rabbits were treated starting 8 h
post-infection with an intravenous regimen of 150 mg/kg
ceftazidime at h 0 and 4, 150/37.5 mg/kg ceftazidime-
avibactam at h 0 followed by 150 mg/kg ceftazidime at h 4,
or 125 mg/kg meropenem at h 0 and 4. Five rabbits were
used per treatment and control group and cerebrospinal
fluid (CSF) was sampled at 0, 1, 2, 4, 6 and 8 h following
start of treatment. Both the ceftazidime-avibactam regimen
and the meropenem regimen were found to be bactericidal
([3 log10 CFU reduction in CSF from initial values) 5 h
after start of treatment. Eight h after start of treatment, CSF
CFU levels were reduced by 0.10 ± 0.45 for ceftazidime,
4.23 ± 0.60 for meropenem, and 5.66 ± 0.83 for the
ceftazidime-avibactam regimen. By two-tailed Fisher exact
test, the meropenem and ceftazidime-avibactam regimens
were reported as significantly different from the ceftazi-
dime regimen (p \ 0.05) and the ceftazidime-avibactam
regimen was reported as significantly different from the
meropenem regimen (p \ 0.05).
In summary, these animal studies show that ceftazidime-
avibactam is effective in a variety of animal infection
models including murine septicaemia, murine kidney
infection, neutropenic murine thigh infection, neutropenic
murine pneumonia and rabbit meningitis, infected with a
variety of b-lactamase-producing organisms including
ESBL, KPC and AmpC. More studies are required to assess
the optimal way to administer ceftazidime-avibactam and
the optimal pharmacodynamic parameters to optimize
efficacy and minimize resistance selection.
9 Clinical Trials
The results of two ceftazidime-avibactam phase II clinical
trials have been published to date (Table 7) and are
170 G. G. Zhanel et al.
reviewed. A prospective, international, multicentre, dou-
ble-blinded, randomized (1:1) trial compared safety and
efficacy of ceftazidime-avibactam (2,000/500 mg) plus
metronidazole (500 mg) with meropenem (1,000 mg), each
administered intravenously three times daily for the treat-
ment of complicated intra-abdominal infection in hospital-
ized adults (NCT00752219) [95]. Male and female patients
aged 18–90 years with indications of complicated intra-
abdominal infection (including infection in the appendix
47.3 %, stomach/duodenum 25.6 %, colon or small bowel
17.2 %, gall bladder, liver or spleen 9.4 %) caused by
organisms determined to be susceptible to either treatment
arm and requiring surgery and antibacterial therapy, were
recruited if they were free of sepsis, did not have abnormal
liver function tests (ALT, AST alkaline phosphatase [AP] or
bilirubin [3 times the upper limit of normal) or impaired
renal function (CLCR \50 mL/min), were not immuno-
compromised, had Acute Physiology and Chronic Health
Evaluation (APACHE)-II scores B25, were expected to
survive for the entire study period, and had not had systemic
antibacterials within 72 h pre-study (with the exception of
previous failed therapy or surgical prophylaxis for less than
24 h). Both ceftazidime-avibactam plus metronidazole and
meropenem regimens (Table 7) were administered for
5–14 days. A total of 203 patients were initially enrolled in
the study, with 68 patients clinically evaluable for ceftazi-
dime-avibactam plus metronidazole and 76 for meropenem
at the end of the study. Patients did not finish the study for a
variety of reasons, including patient withdrawal, protocol
violation, lost to follow-up and adverse effects (no differ-
ences between treatment arms). Favourable clinical
response rates (complete resolution or significant improve-
ment of the signs and symptoms of infection 2 weeks after
the last treatment dose) were 91.2 % (62/68) for patients
receiving ceftazidime-avibactam plus metronidazole and
93.4 % (71/76) for patients receiving meropenem. Response
rates were not significantly different (p = 0.60). Microbio-
logical eradication was considered equivalent to favourable
clinical response. The most common pathogens isolated
included Enterobacteriaceae (89.7 % in the ceftazidime-
avibactam plus metronidazole arm) and 92.1 % in the
meropenem arm. For patients found to have one or more
ceftazidime-resistant (MIC[8 mg/L) Gram-negative bacilli,
a favourable microbiological response was achieved in 96.2
% (25 of 26) of patients in the ceftazidime-avibactam plus
metronidazole arm and 94.1 % (16 of 17) of patients in the
meropenem arm. Adverse effects occurred in 15 % of
patients in the ceftazidime-avibactam plus metronidazole
arm and 17 % of patients in the meropenem arm.
A prospective, international, multicentre, investigator-
blinded, randomized (1:1) study compared safety and
efficacy of ceftazidime-avibactam (500/125 mg) adminis-
tered three times daily (30-min infusion) to imipenem/ Ta
ble
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Ceftazidime-Avibactam 171
cilastatin (500 mg) administered four times daily (30-min
infusion), for the treatment of complicated urinary tract
infections, including acute pyelonephritis in hospitalized
adults (NCT00690378) [96]. Recruited patients were males
and females aged 18–90 years with documented acute
pyelonephritis (59.7 %) or other complicated urinary tract
infection (40.3 %) caused by Gram-negative organisms not
resistant to one or both study drugs. Patients were excluded
if they had received more than one dose of a potentially
effective antibacterial within 48 h prior to admission urine
culture (or any doses after culture), had an ileal loop,
vesicoureteral reflux, complete obstruction of any portion
of the urinary tract, perinephric or intrarenal abscess, a
permanent indwelling catheter or nephrostomy, or a history
of hypersensitivity to either study medication. Both ceft-
azidime-avibactam and imipenem/cilastatin (Table 7) were
administered for 7–14 days. Patients meeting pre-defined
clinical criteria for improvement (afebrile C24 h, resolu-
tion of nausea and vomiting, improved signs and symp-
toms) after a minimum of 4 days of either therapy were
switched to oral ciprofloxacin 500 mg every 12 h, or
an appropriate oral alternative if necessary (maximum
14 days). A total of 135 patients received study therapy,
of whom 62 were microbiologically evaluable (27 in the
ceftazidime-avibactam arm and 356 in the imipenem arm).
Clinically evaluable patients included 28 in the ceftazi-
dime-avibactam arm and 36 in the imipenem arm. Patients
were excluded from the clinical and microbiologically
evaluable populations mainly due to lack of an isolated
pathogen (23 in the ceftazidime-avibactam group, 19 in the
imipenem/cilastatin group). Favourable microbiological
response was the primary outcome, defined as both eradi-
cation of pathogens in the urinary tract (reduction of levels
in the urine from C105 CFU/mL to\104 CFU/mL) and no
pathogens in the blood at a follow-up 5–9 days after
completion of therapy. Favourable clinical response was a
secondary outcome, defined as resolution of all or most
pre-therapy signs and symptoms, with no further (non-
study) antibacterial required. Favourable microbiological
response rates were 70.4 % for the ceftazidime-avibactam
arm and 71.4 % for the imipenem/cilastatin arm. Favour-
able clinical response rates were 85.7 % for the ceftazi-
dime-avibactam arm and 80.6 % for the imipenem/
cilastatin arm. Microbiological response rates were not
significantly different (95 % CI difference of -27.2 % to
25.0 %), but the significance of clinical response rate was
not tested. Six of seven patients in the ceftazidime-avi-
bactam arm and 9 of 11 patients in the imipenem/cilastatin
arm had favourable microbiological outcomes against
ceftazidime-resistant pathogens (MIC [8 mg/L). Adverse
effects in this study were reported in 67.7 % of patients in
the ceftazidime-avibactam arm and 76.1 % of patients in
the imipenem/cilastatin arm.
Clinical trials to date suggest that ceftazidime-avibac-
tam is as effective as standard carbapenem therapy in
complicated intra-abdominal infection and complicated
urinary tract infection, including infection caused by ceft-
azidime-resistant Gram-negative bacilli. At the time of
writing, phase III trials are still in progress.
10 Adverse Effects
The safety and tolerability of ceftazidime-avibactam has
been reported in three phase I pharmacokinetic studies and
two phase II clinical studies. In these studies, assessment
was conducted by physical examination, laboratory tests,
vital sign monitoring, ECG recording and recording of
treatment-emergent adverse events [88, 91, 95, 96], except
in one phase I study where adverse events were assessed by
subject interview [97].
In three phase I pharmacokinetic studies encompassing
119 subjects, treatment-emergent events were observed in
14 healthy subjects (one or more per subject). One event,
orthostatic hypotension, was reported as moderate, while
the remainder, including abdominal pain, anxiety, appli-
cation site bruising, dry mouth, dysgeusia, feeling hot,
feeling jittery, headache, hyperhidrosis, postural dizziness,
sense of oppression, and somnolence, were reported as
minor. Four treatment-related events were reported in three
anuric subjects: general discomfort, stomach pain, ructus
and symptoms of hypoglycaemia (in a diabetic patient)
[91]. No subject withdrew from these studies as a result of
an adverse event.
In a phase II study comparing the treatment of compli-
cated intra-abdominal infection by ceftazidime-avibactam
plus metronidazole (safety population 101) and merope-
nem (safety population 102), treatment-emergent events
(drug related or not) reported by 5 % or more patients were
nausea, vomiting, abdominal pain, pyrexia, wound secre-
tion, cough, haematuria and increases in liver enzymes
(ALT, AST, AP), platelet count and white blood cell count
tests [95]. Drug-related adverse effects were reported in 15
% of the ceftazidime-avibactam plus metronidazole arm
and 17 % of the meropenem arm. The types and frequency
of all treatment-emergent adverse effects were similar for
both arms, though it was noted that the ceftazidime-avi-
bactam plus metronidazole arm had a higher number of
gastrointestinal (GI)-tract events (nausea, vomiting,
abdominal pain) and the meropenem arm had a higher
number of liver enzyme elevation events (ALT, AST, AP).
Serious adverse events were observed in nine patients in
the ceftazidime-avibactam and 11 patients in the merope-
nem arm, though only one of these events (elevated liver
enzymes in a ceftazidime-avibactam plus metronidazole
patient) was considered drug related.
172 G. G. Zhanel et al.
In a phase II study comparing the treatment of compli-
cated urinary tract infection by ceftazidime-avibactam
(safety population 68) and imipenem/cilastatin (safety
population 67), treatment-emergent events (drug related or
not) reported by 5 % or more patients were constipation,
diarrhoea, abdominal pain, upper abdominal pain, abdom-
inal distension, headache, dizziness, chest pain, anxiety,
insomnia, injection/infusion site reaction, increased ALT
levels, back pain and hypertension [96]. Drug-related
adverse effects were reported by 35.3 % of patients in the
ceftazidime-avibactam arm and 50.7 % of patients in the
imipenem/cilastatin arm, though it should be noted that
adverse events continued to be recorded after conversion to
oral therapy following clinical improvement (see ‘‘Clinical
Trials’’ section). Serious drug-related adverse events were
reported for three patients in the ceftazidime-avibactam
arm (accidental overdose, diarrhoea, renal failure) and one
in the imipenem/cilastatin arm (increased serum creati-
nine). The overdose caused no sequelae.
A double-blind, randomized, placebo-controlled, four-
way crossover, phase I study conducted in a single centre
investigated the effect of a supra-therapeutic dose of ceft-
azidime-avibactam on cardiac depolarization [98]. Non-
smoking male subjects (n = 51) with median age 26 years
(range 18–45) and median body mass index (BMI) 26.5 kg/
m2 (range 19.4–30.0) were enrolled in the study; 43 were
evaluable. Subjects received four treatments in random
order (with minimum 3-day washout between treatments):
a 30-min infusion of 3,000/2,000 mg ceftazidime-avibac-
tam following a 30-min infusion of saline placebo; a
60-min infusion of 1,500/2,000 mg ceftaroline fosamil-
avibactam administered as two 30-min infusions; saline
placebo administered as two 30-min infusions; a single,
open-label, oral dose of 400 mg moxifloxacin as active
control. Primary outcome was Fridericia-corrected QT
interval; ECG values (heart rate and RR, PR, QRS and QT
intervals) were also assessed at 0, 0.5, 1, 1.5, 2, 3, 4, 6, 8,
12 and 24 h. Ceftazidime-avibactam was found not to
significantly elevate the Fridericia-corrected QT interval,
and observed ECG values were similar for ceftazidime-
avibactam and placebo. Compared with moxifloxacin,
ceftazidime-avibactam was found to result in significantly
lower elevations in the Fridericia-corrected QT interval.
Urticaria (in one patient) was the only reported non-mild
adverse event related to ceftazidime-avibactam. Eleven mild
adverse events experienced by patients in the ceftazidime-
avibactam group were reported by system-organ-class: four
skin/soft tissue disorders, three GI tract disorders, three
administration-site conditions and one cardiac palpitation.
No abnormalities were observed in vital signs, laboratory
tests or physical examinations.
To date, ceftazidime-avibactam appears to be well tol-
erated in healthy subjects as well as patients with infectious
diseases, with few serious drug-related treatment-emergent
adverse events reported.
11 Place of Ceftazidime/Avibactam in Therapy
The addition of avibactam restores the activity of ceftazi-
dime against Gram-negative bacilli that achieve b-lactam
resistance through expression of the Ambler class A ES-
BLs, chromosomal or mobile class C b-lactamases, serine
carbapenemases, or some class D b-lactamases. Safety and
pharmacokinetic results published to date suggest that no
additional considerations need to be taken when dosing
ceftazidime-avibactam compared with ceftazidime alone.
Ceftazidime-avibactam has demonstrated clinical efficacy
similar to that of carbapenem therapy in phase II studies of
complicated intra-abdominal infection and complicated
urinary tract infection (including acute pyelonephritis). The
extensive clinical experience with ceftazidime and the
knowledge that avibactam broadens the spectrum of ceft-
azidime versus ß-lactamase-producing Gram-negative
bacilli, will provide clinicians with confidence in using this
agent. To date, no data are available on the efficacy of
ceftazidime-avibactam for the treatment of difficult-to-treat
infections such as hospital-acquired and ventilator-acquired
pneumonia. The exact roles for ceftazidime-avibactam in
the treatment of infectious diseases will, in part, depend on
the development of other b-lactam/b-lactamase inhibitor
combinations including ceftaroline-avibactam, imipenem-
MK7655 and ceftolozane-tazobactam. An important
advantage of ceftazidime-avibactam is that its development
is furthest along and it may be first to market.
Potential future roles for ceftazidime-avibactam include
the treatment of suspected or documented infections caused
by resistant Gram-negative bacilli-producing ESBL, KPC
and/or AmpC b-lactamases. In addition, ceftazidime-
avibactam may be used in combination (with metronidazole)
for suspected polymicrobial infections. Finally, the increased
activity of ceftazidime-avibactam versus P. aeruginosa
may be of clinical benefit in patients with suspected or
documented P. aeruginosa infections.
Acknowledgments Dr George G. Zhanel has received research
funding from AstraZeneca. No other conflicts are reported for the
other authors. Chris Lawson was supported by a summer studentship
paid in part by the University of Manitoba and AstraZeneca. The
authors would like to thank AstraZeneca for their assistance in
developing the ceftazidime-avibactam bibliography.
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